construction defects, failures, and repairs (i.e. learn...

Construction Defects, Failures, and Repairs

(i.e. Learn From the Mistakes of Others)

Paul J. Bennett, MS, PE, CBIEManaging Engineer

Introductions

•Paul Bennett, M.S., P.E., CBIE– Managing Engineer

•Residential & Commercial Design & Construction

•2008 Outstanding Professional of the Year Award for Larimer County

•Failure Investigation

Introductions

• Who Are You?

Learning Objectives

At the end of this program, participants will be able to:

1. Students will understand how to correctly apply the 2012 IBC and IEBC to repairs of damaged structures

2. Students will understand the most common construction defects and how to prevent them as designers, builders, plan reviewers, and inspectors

3. Students will learn how to prevent future damages from various case studies

environmental • failure analysis & prevention • health • technology development

A leading engineering & scientific consulting firm dedicated to helping our clients solve their technical problems.

Masters33%

Doctorates50%

Bachelors17%

Consulting Staff

Exponent Offices

Derby andHarrogate DüsseldorfHangzhou

Boston:• Maynard• Natick

Chicago:• Downtown Chicago• Warrenville

Denver

Detroit

Houston

Miami

New YorkPhiladelphia

Phoenix

Seattle

Southern California:• Irvine• Los Angeles

Washington, DC:• District of Columbia• Maryland• Virginia

San Francisco Bay Area:• Menlo Park• Oakland

Basel

Atlanta

Introductions

•Hot Dogs and Attorneys

Lesson Plan

• Repair Solutions and Guidelines– Ch 34 IBC and IEBC– Case Studies in Applying IEBC

• Importance of Studying Failures– Famous Failures

• Most Common Types of Construction Defects Case Studies– Ventilation– Moisture Intrusion (Building Envelope Failure)– Structural

Code Background

• Why do Building Codes Even Exist?– Aren’t they in place just to make the

building cost more?– Or are they in place to protect innocent

bystanders?

Code Background

• Purpose– Minimum Requirements for Public Safety

• History– Fire– Stability– Life Safety

Code Background

Code Background

Repair Design

• Is the Code silent?

• IRC Appendix J

• 2012 IBC (CH 34)

• 2012 IEBC

Repair Design

• Problem: No consistency among design professionals when evaluating existing buildings

• Solution: Chapter 34/IEBC

• Designers and Officials:– Understand what the Codes Require– Apply it and Enforce it

• Designers:– You can ask for more but make clear it is

voluntary– Don’t be the EOR if you don’t like it

Repair Design

• Some major changes to the repair design chapters in the ’12 code

Fundamental Questions

• What Repairs Are Necessary To Restore The Structure To Pre-loss Condition ?

• Upgrades To Elements That Have Sustained Direct Physical Damage

• Upgrades To Undamaged Building Elements

• Code-upgrades

Repair Solutions Per IBC and IEBC

• Pandora's Box

• Where do you stop??

• What does the Code say??

Building Codes

• 1997 Uniform Building Code (UBC)

• 2003 International Building Code (IBC)




UBC Repair Provisions

• 1997 UBC– Chapter 34 – Cannot Create An Unsafe Condition

• Cannot Increase Loads On Structural Components Beyond Their Capacity

• Cannot Obstruct Egress• Cannot Reduce Fire Resistance

IBC Definitions

• What is an existing building?– A structure erected prior to the date of

adoption of the appropriate code, or one for which a legal building permit has been issued – 2006, 9, 12 IBC and IEBC

– Chapter 2 in 2012

IBC Chapter 34 Overview

– 3404.2 Flood hazard areas must be upgraded if the repairs or alterations are a “substantial improvement” • Note: Substantial improvement can be

triggered by substantial damage• 2003,2006,2009,2012 IBC


• 2003, 2006 Section 3403 Additions, Alterations or Repairs– 3403.2 Structural

• Additions or alterations to an existing structure shall not increase the force in any structural element by more than 5 percent, unless the increased forces on the element are still in compliance with the code for new structures, nor shall the strength of any structural element be decreased to less than that required by this code for new structures. Where repairs are made to structural elements of an existing building, and uncovered structural elements are found to be unsound or otherwise structurally deficient, such elements shall be made to conform to the requirements for new structures.


• Historic Buildings Section 3409

• Definition:– Buildings that are listed in or eligible for listing on

the National Register of Historic Places or designated historic under an appropriate state or local law.

• Provisions not applicable where the AHJ has determined the building does not constitute a distinct life safety hazard.

• Flood hazard rehabilitation not required for substantial improvement if Historic


• Section 3403 Additions, Alterations or Repairs– 3403.1 Portions of the structure not altered and

not affected by the alteration are not required to comply with the code requirements of a new structure.

– 2003,2006 IBC– Much Different in 2009 IBC

IBC Repair Provisions

• 2009, 2012 IBC Repairs

• Repaired Elements Shall Be Upgraded

• Provisions For Undamaged Components

IBC Upgrades

• 2009, 2012 IBC Chapter 34, Very different chapter

• A new repair section is now in place– Explicit that new and replacement

materials must meet current code, 3401.4.2

IBC Upgrades

• 2009, 2012 IBC Chapter 34, Very different chapter– Substantial Structural Damage to:

• Lateral System –Entire building must be rehabilitated

to be in conformance with the new code

• Gravity System–Only the damaged members and

those that receive loads from them need to be upgraded

IBC Upgrades

• 2009, 2012 – New Definitions for Dangerous– Dangerous conditions upgrades are up

to the Building Official– Reads like 2006 IEBC

IBC Upgrades

• 2012 Chapter 34 IBC

• Prior to 2009 There was no Definition of Dangerous in IBC, see IEBC

Dangerous Building

• IEBC Section 202; 2003,2006 IEBC– Definition Of Dangerous

IBC Upgrades

• 2009, 2012 Chapter 34 IBC –Dangerous:

IBC Upgrades

• Dangerous in 1991 UCADB:

IBC Upgrades


IBC Upgrades


Dangerous Buildings

Dangerous Buildings

Dangerous Buildings

IBC Upgrades

• 2012 Chapter 34 IBC

IBC Upgrades

• 2012 Chapter 34 IBC - Changes

• SSD Definition, Changed from 20% to 33%

IBC Upgrades

• 2012 Chapter 34 IBC– What if SSD is not Triggered?– No Problem, Repair in Place 3405.4

IBC Upgrades


• Less than SSD, Clarified its Material Strengths we are Using.

IBC Upgrades


• SSD to Lateral System

IBC Upgrades


• What if SSD to Lateral System?

IBC Upgrades


• New Exceptions

IBC Upgrades

• 2012 Chapter 34 IBC -

IBC Upgrades

• 2012 Chapter 34 IBC -

IBC Upgrades

• 2012 Chapter 34 IBC – Changes

• What if SSD to Gravity System?

IBC Upgrades


• What if SSD to Gravity System?

IBC Upgrades


• What About Fires, Decay, Vehicle Impact?

• 2015 Code Cycle

Code Upgrade Controversy

• What if only one member broke but the remaining members look likely to collapse?

• This still meets the definition of dangerous in 2009 and is up to AHJ


• A dilemma is presented:– If only 20% of the building is damaged by

a major event, isn’t that what we hoped for?


• A dilemma is presented:

• ASCE 7-05 Section 1.4 “capable of resisting those loads without collapse”

• Life Safety: Structural damage without partial or total collapse which might pose a risk to life

• Collapse Prevention: Damage (structural or non-structural) which exceeds 30% of replacement value


• Engineering analysis:– How can you investigate a structure

without destructive testing?– Usually you can find ways– Assumptions may have to be made


• For 2009:– The engineer is not required to evaluate

more than the damaged member unless SSD thresholds are triggered

– Dangerous is much more liberal and is not mandated to be abated

– This solves the Denver snow example dilemma

– But new dilemma’s are created, such as:


•What about: snow load causes damage.

Case Study – Unreinforced Masonry

Investigation

• Jurisdiction has accepted IEBC– Qualifies as dangerous– Qualifies as substantial structural damage– Rebuild entire structure

• If chapter 2006 IBC Ch 34 were used:

– Repair damage per IBC


– Lessons Learned• Unreinforced masonry structures will often

require great repairs under this code


– Masonry Building, SDC ‘D’– Partial Roof Collapse Under Snow Loads– Which Code?

Dangerous?

• Historic Building

• Two Previous Fires

Dangerous?

Dangerous?

Dangerous?

Dangerous?

Dangerous?

The Study of Failures

Importance of Failures

• Importance of studying failures

• We Learn From our Past Mistakes– GEN X & Y don’t believe it until you prove

it

Caveats

• A view from the dark side– Overall performance of our building

stock is excellent – catastrophic failures are rare

– Performance, financial, and aesthetic failures are all too common

• Failures are powerful learning tools– Reminder of our responsibilities – Reminder of fallibility of our systems– Advance understanding and practice

• Structure-centric

The Code of Hammurabi – 1730BC

• If a builder builds a house for some one, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death.

Failure Trajectory

For want of a nail,the shoe was lost.

For want of a shoe, the horse was lost.

For want of a horse,the rider was lost.

For want of a rider,the battle was lost.

For want of a battle,the kingdom was lost.And all for the wantof a horseshoe nail.

The Devil is in the Details –Mighty Failures From Little Acorns Grow

A Designer’s Worst Nightmare

Famous Failures

• Hyatt Regency Walkway– Walkways suspended by six 32mm

hanger rods– Opened in 1980, 4 years to construct– July 17, 1981, 2000 ppl on atrium and

walkways– Walkways collapsed, 114 killed, 200+

injured

Famous Failures

Famous Failures

Hyatt Regency Walkway, Kansas City, MO – 7.17.81

Hyatt Regency

Design Phase – Bridge Connection

•No rod size

•No reaction

•No rod strength

• Changes During Shop Drawings– Requested two rods by phone– Approved by phone with caveat “submit

through channels”

Design Drawings vs. Shop Drawings

The shop drawings are checked by a technician who did not work on the project. Questions are raised about the strength of the rod.

• THIS CONNECTION WAS NEVER DESIGNED, NEVER DRAWN AND NEVER SUBMITTED FOR APPROVAL

Design Drawings vs. Shop Drawings

Famous Failures

• Investigation revealed:– An impractical original design– No redundancy– Engineer approved contractor’s change

without performing calculations– Connection was near failure with just

dead load– Even if the detail wasn’t changed it likely

would have failed due to inadequate bearing area

Famous Failures

• Lessons Learned– Redundancy is a good thing– Failures often occur at small

connections, not big picture items– Peer review needs to be thorough

World Trade Center Towers

• Design & Construction 1962 – 1973

• 110 Stories

• 1362/1368’ Tall

• Tallest buildings constructed since Empire State Bldg in 1932

• 9,500,000 Sq. Ft.

• Designed to withstand impact of B-707

• Public Works Project

World Trade Center Towers

• First use of wind tunnel for design

• Research regarding human tolerance for motion

• First use of structural dampers

• First use of computer for design

• Very lightweight structures

• First use of sky lobbies• Many more…

Lightweight, highly optimized structure

Modular Construction

• Trees fabricated in shop, transported to site and erected

• Tree modules staggered to offset column splices

• Floors were 4-inch lightweight concrete over 1-1/2-in. metal deck (22 gauge)

• Modular fabrication and erection techniques

• Three story high columns connected by deep spandrel plates (Trees)

Impact and Damage to WTC 2• 78th to 84th floor affected

• 33 exterior columns severed; 1 heavily damaged

• 10 core columns severed; 1 heavily damaged

• 39 of 47 core columns stripped of insulation on one or more floors.

• Insulation stripped from trusses covering 80,000 ft2 of floor area.

• Structure retained integrity and strength for 56 minutes

Simulation of Damage to WTC 2

Why not immediate collapse?

Redundancy & Redistribution of LoadThis image cannot currently be displayed.

Redistribution of Load

• Column strains before and 10 minutes after impact on WTC-1

schematic of hat truss

Why Ultimate Collapse?

Fire Ignition

• At impact, each aircraft contained ~10,000 gallons of fuel

• Between 1,000 and 3,000 gallons of fuel consumed in fireballs

• Rest flowed down tower or remained on impact floors

• Most of remaining jet fuel consumed within first few minutes of fire

• Burning fuel ignited combustibles present on affected floors

Fire Development

• Since fire protection systems compromised, fire development and growth was unchecked

• Ceiling temperatures approximately 800 – 2000 oF (depending on location, fuel load, and ventilation)

• High temperatures heated structural steel within towers

Structural Response to Fire Loading

• Impact compromised fireproofing• Elevated stress on columns due to

impact and destroyed elements• Portions of framing directly below

partially collapsed area carried substantially greater loads

• Fire spread and raised temperatures further weakened structure until unable to support weight.

Structural Response to Fire Loading

• As floor framing and slabs heated, they expanded

• Floor framing lost rigidity and began to sag (catenary action)

• Increase load on floor below and lateral column instability

• Temperature of column steel increased, yield strength and modulus of elasticity degraded and critical buckling strength of columns decreased (especially with core columns)

Progression of Collapse

• As unsupported height of freestanding columns increased, they buckled at bolted column splice connections and collapsed

• Initiation of collapse converted potential energy into kinetic energy

• Progressive failure as floors above accelerated and impacted floor below

OK City & WTC Lessons

• Increased attention to Progressive Collapse (Disproportionate Collapse)

• Increased attention to relationship between fire ratings and structural systems

• Increased attention to fire safety in highrises

OK City & WTC Lessons

• Collapse mechanisms are readily explainable if structural systems are understood

• No need for, nor legitimate evidence of, any conspiracy related to structural damage and collapse

Closure

• Most failures are a sequence or intersection of multiple events and are preceded by warning signals– Heeding warning signals averts failure!

• The Devil is in the details – A chain is only as strong as its weakest

link!

• Innovate and create, but– Be skeptical

Case Studies in Failures

Construction Defect Case Studies!!



Construction Defects

Moisture Intrusion


“As every dam engineer knows, water also has one job, and that is to get past

anything in its way” – Macauley 2000

Moisture Intrusion

• Building science– Many materials are porous– Know the product, EIFS, Stucco,

Flashing, Roofing, ect..– Ask for installation instructions

Case Study – Moisture Intrusion

• Background– 3 Year Old Home– $1.1 Million– Above Grade Deck with Outdoor Living

Area Below– Water Damage to Soffit Below Deck and

Walk Out Basement– EIFS Bulging– Rim Joist EIFS Detaching


• Background:– Finished Above Grade Deck






Ventilation

Inadequate Ventilation

• Attic Ventilation– First Required in 1964 UBC

• “Enclosed attics shall have clear ventilation area to the outside of not less than one square inch (1 sq. in.) per ten square feet (10 sq. ft.) of horizontal attic area.”


• Attic Ventilation Code Changes– 1967 UBC

• Cross Ventilation

– 1991 UBC• Vapor Barriers


• Language in the Code:

“The net free ventilating area shall not be less than 1/150 of the area of the space ventilated, except that the area may be 1/300 provided at least 50 percent of the required ventilated area is provided by ventilators located in the upper portion of the space to be ventilated at least three feet (3’) above eave or cornice vents.”


• Why ??– Summer

• Heat Build Up In Daytime– +70 Degrees

• Cool Down At Night– Adds Moisture Into Insulation


• National Design Specification (Wood Code)– Sustained exposure to elevated temperatures

up to 150 degrees results in up to a 50% decrease in the structural capacity of a wood member.


• National Design Specification (Wood Code)– Sustained moisture contents of greater than

19% results in up to a 33% decrease in the structural capacity of a wood member.

– Elevated Temperatures and Moisture Content results in accelerated “creep” deflection.

Attic Ventilation





• Summary– Heat-Cool Cycle

• Causes Condensation– Reduces Strength of Wood– Causes Wood to Rot– Causes Wood to Deflect

Case Study – Inadequate Ventilation• Background

– 7 Year Old Commercial Buildings– Smells Musty

Case Study – Inadequate Ventilation




Case Study – Inadequate Ventilation• Lessons Learned

– All attic areas need ventilation– Accomplished GC’s make mistakes

Case Study – Inadequate Ventilation• Background

– 7 Year Old Home– Stick Framed Roof– Depressions in Roof– I’ve Been Doing in That way for 30

years….



Case Study – Inadequate Ventilation• Lessons Learned

– Stick Framed Roofs Need Ventilation– Past Experience is Not Always a Good

Indication of Future Performance


Structural


• “When utilizing past experience in the design of a new structure we proceed by analogy and no conclusion by analogy can be considered valid unless all the vital factors involved in the cases subject to comparison are practically identical. Experience does not tell us anything about the nature of these factors and many engineers who are proud of their experience do not even suspect the conditions required for the validity of their mental operations. Hence our practical experience can be very misleading unless it combines with it a fairly accurate conception of the mechanics of the phenomena under consideration.”

- Karl Terzaghi 1939

Case Study – Structural

• Background– Recently Completed Riding Arena– PEMB– SNOW!!– RAM Tough™

PEMB Design: EOR

• Really That Important?

PEMB Design: EOR

• Answer is… YES!

• Engineer-of-Record (EOR):– Design Load Oversight– Coordination Between Trades and

Engineers– Coordination Between Engineers


• Lessons Learned– Dodge’s are strong– Knowledge of AutoCad...– Understand PEMB’s– EOR is CRITICAL!!!


• Background– PEMB – Snow Load Problems


• Alleged Defects– Inadequate Resistance to Snow Load– Inadequate Foundations– Design Errors


• Issues:– Large Expansive Roofs and Drifting– Ground Snow vs. Roof Snow– Failure in 2003, 2006– Reduction of Snow Loads (0.7)– Importance Factor– ASD vs. LRFD– Unique Design of Moment Frames– Load Paths



• Background– PEMB – Aircraft Hanger


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